Nowadays, vehicle door handles are equipped with devices for detecting a user's intention to lock or to unlock a vehicle door. Detecting a user's intention to lock/unlock, coupled with the recognition of an identifier contained in a “hands-free” access device, for example a remote-control access “hands-free” electronic fob, or a mobile telephone, carried by this user, makes it possible to remotely lock and unlock opening elements of the vehicle. Thus, when the user, carrying the electronic fob or the corresponding telephone identified by the vehicle, wishes to unlock the vehicle, he approaches the handle or touches the door handle of the vehicle, and the opening elements of the vehicle are then automatically unlocked. By approaching or by pressing on a precise location of the door handle of the vehicle, called “unlocking zone”, the door (or alternatively all of the opening elements) is (are) unlocked without any other action from the user. Conversely, when the user, still carrying the necessary fob identified by the vehicle, wishes to lock his vehicle, he closes the door of his vehicle and he approaches or momentarily presses on another precise location of the handle, called “locking zone”. This movement makes it possible to lock the opening elements of the vehicle automatically.
These detection devices generally comprise two capacitive sensors, in the form of two electrodes connected electrically to a printed circuit and integrated into the door handle, each in a precise locking or unlocking zone. Generally, one electrode is dedicated to each zone, that is to say one electrode is dedicated to detecting the approach and/or the contact of the user's hand in the locking zone and one electrode is dedicated to detecting the approach and/or the contact of the user's hand in the unlocking zone.
The locking/unlocking detection device furthermore comprises a radiofrequency antenna for exchanging an identifier between the vehicle and the hands-free access fob or the telephone.
This antenna may be of low-frequency (LF) type, for example at 125 kHz.
If the portable device is a mobile telephone, radiofrequency and LF communication with the vehicle is not always possible, since most mobile telephones do not have any RF, or LF, communication means whose frequencies are compatible with those used during communication with a vehicle, such as the frequencies of 315 MHz and 433.92 MHz for RF and 125 kHz for LF.
However, mobile telephones now employ the Bluetooth® or Bluetooth Low Energy “BLE” communication standard, that is to say communication at ultra-high frequency (UHF) from 2.4 GHz to 2.48 GHz. This communication standard exhibits the advantage of being universal and therefore does not require any accreditation specific to each country (only a Bluetooth Low Energy international certification), as is the case with the current RF and LF communication standards whose operating frequency differs according to country.
It therefore becomes necessary to adapt the “hands-free” access and/or starting system to a vehicle so that it is also able to operate with a mobile telephone equipped with the Bluetooth® communication standard and no longer solely by way of radio waves and low-frequency waves (RF, LF).
The advantage of the Bluetooth® communication standard or of Bluetooth Low Energy BLE is that it allows a large communication range of about 100 m around the vehicle for BLE.
Bluetooth® communication therefore exhibits numerous advantages with respect to low frequency.
The detection device is connected to the vehicle's electronic computer (ECU: abbreviation for “electronic control unit”) and sends it a presence detection signal. The electronic computer of the vehicle has, beforehand, identified the user as being authorized to access this vehicle, or alternatively, following the reception of this presence detection signal, it performs this identification.
As explained above, when the “hands-free” access device is a mobile telephone, the identifier is exchanged through Bluetooth® communication.
If the electronic computer recognizes the identification code as the one authorizing access to the vehicle, it triggers the locking/unlocking of the door (or of all of the opening elements). If, on the other hand, the electronic computer has not received any identification code or if the received identification code is erroneous, locking or unlocking is not performed.
Such vehicles are therefore equipped with door handles comprising a detection device, itself comprising a high-frequency or ultra-high-frequency (HF or UHF) antenna A, and two electrodes connected to a microcontroller, integrated into a printed circuit and supplied with a voltage.
Purely for the sake of explanation, consideration will be given here to a detection device D comprising two capacitive sensors in the form of two electrodes, one electrode dedicated to the unlocking zone and one electrode dedicated to the locking zone, said two electrodes being connected to a printed circuit comprising a microcontroller, and a Bluetooth® antenna A. A detection device D from the prior art is described with reference to FIG. 1.
FIG. 1 shows a motor vehicle door P handle 100 (vehicle not shown) in which there is situated a device D for detecting the presence of a user. Said door P handle 100 comprises a first outer surface S1 oriented in the direction of the door P and a second outer surface S2, opposite the first outer surface S1 and therefore oriented on the side opposite the vehicle, more precisely toward the user (not shown). This detection device D comprises a first unlocking electrode E2, one face of which is situated close to the first outer surface S1, and control means 60 and a UHF antenna A, one face of which is situated close to the second outer surface S2, a second locking electrode E1, one face of which is situated close to, the second outer surface S2, and control means 60. The first and the second electrode E1, E2 are connected to the control means 60. These control means 60 measure the capacitance between the terminal of each first and second electrode E1, E2 and ground, formed by the hand of the approaching user, so as to detect the presence (the approach and/or the contact) of a user in the detection zones, that is to say in a locking zone Z1 or in an unlocking zone Z2, and consist for example of a microcontroller 60 integrated into a printed circuit 80. The high-frequency antenna A is for its part connected to an electronic computer on board the vehicle (not shown) of BCM (“body controller module”) type, which manages the identification requests transmitted by said ultra-high-frequency antenna A.
When the user's hand M approaches the electrode E1 or E2, the user acts as a second electrode, connected to ground, which increases the capacitance of the detection capacitance to a capacitance higher than the nominal capacitance of the detection capacitance “at rest” (that is to say in the absence of a user).
The move in the capacitance above a threshold confirms the detection of the approach of the user's hand.
However, this detection device D from the prior art exhibits major drawbacks.
Specifically, the detection of the approach of a user using capacitive sensors (first and second electrode E1 and E2) is not robust and generates false detections.
In particular, in some environmental conditions, when the ambient air is humid or when there is salt on the roads, capacitive coupling is created between the detection zones (locking zone Z1 and unlocking zone Z2) and the metal parts of the vehicle, thereby preventing any detection of the presence of a user using the capacitive sensors.
In addition, raindrops or snowflakes on the door handle increase the capacitance measured by the capacitive sensors, thus triggering false detections.
Other drawbacks stem from the cost incurred by the device (the two electrodes are made of copper) and by the space necessary inside the handle in order to house the detection device therein.